Method and apparatus for vehicle service system optical target assembly

Abstract

A machine vision vehicle wheel alignment system for acquiring measurements associated with a vehicle. The system includes at least one imaging sensor having a field of view and at least one optical target secured to a wheel assembly on a vehicle within the field of view of the imaging sensor. The optical target includes a plurality of visible target elements disposed on at least two surfaces in a determinable geometric and spatial configuration. A processing unit in the system is configured to receive at least two sets of image data from the imaging sensor, with each set of image data acquired at a different rotational position of the wheel assembly around an axis of rotation and representative of at least one visible target element on each of the two surfaces, from which the processing unit is configured to identify said axis of rotation of the wheel assembly.

1. A machine vision vehicle wheel alignment system for acquiring measurements associated with a vehicle, comprising:
 at least one imaging sensor having a field of view; 
 at least one optical target secured to a wheel assembly on a vehicle within the field of view of said at least one imaging sensor, said optical target having a plurality of visible target elements disposed on at least two surfaces in a determinable geometric and spatial configuration; 
 a processing unit configured to receive at least two sets of image data from said at least one imaging sensor, each set of image data acquired at a different rotational position of the wheel assembly around an axis of rotation, and are representative of at least one visible target element on each of said two surfaces; and 
 wherein said processing unit is further configured to process said received sets of image data, together with said determinable geometric and spatial configuration of said plurality of visible target elements, to identify said axis of rotation of the wheel assembly. 
 
     
     
       2. The machine vision vehicle wheel alignment system of  claim 1  wherein said at least two surfaces are non-planar surfaces. 
     
     
       3. The machine vision vehicle wheel alignment system of  claim 1  wherein said at least two surfaces are smoothly curved surfaces. 
     
     
       4. The machine vision vehicle wheel alignment system of  claim 1  wherein said at least two surfaces are angled surfaces. 
     
     
       5. The machine vision vehicle wheel alignment system of  claim 1  wherein said at least two surfaces are dimensionally stable. 
     
     
       6. The machine vision vehicle wheel alignment system of  claim 1  wherein said at least two surfaces are facets of a dimensionally stable object. 
     
     
       7. The machine vision vehicle wheel alignment system of  claim 1  wherein one of said at least two surfaces of said optical target secured within said field of view is positioned both below, and in front of, an axis of rotation of the vehicle wheel assembly. 
     
     
       8. The machine vision vehicle wheel alignment system of  claim 1  wherein said processing system is configured to identify an intersection point between the axis of rotation of the wheel assembly and a plane of a surface of said optical target. 
     
     
       9. The machine vision vehicle wheel alignment system of  claim 8  wherein said processing system is further configured to identify a wheel center point from said identified intersection point and said determinable configuration of said optical target. 
     
     
       10. The machine vision vehicle wheel alignment system of  claim 8  wherein said intersection point is identified as an common point on a pair of lines of intersection between said plane of said optical target surface at a first rotational position about said wheel axis of rotation, and said plane of said optical target surface at a second rotational position about said wheel axis of rotation, wherein each of said lines of intersection is determined in a discrete coordinate system associated with said first and second rotational positions, respectively. 
     
     
       11. A vehicle wheel alignment system, comprising:
 at least one imaging sensor having a field of view; 
 an optical target secured to a wheel assembly on a vehicle within the field of view of said at least one imaging sensor, said optical target having a plurality of visible target elements disposed on at least two surfaces in a determinable geometric and spatial configuration; 
 a processing unit configured with operating instructions to receive image data from said at least one imaging sensor, said image data representative of at least one visible target element on each of said two surfaces for at least two different rotational positions of said wheel assembly; and 
 wherein said processing unit is further configured with operating instructions to process said received image data, together with said determinable geometric and spatial configuration of said plurality of visible target elements, to establish a three-dimensional vector corresponding to an axis of rotation of the wheel assembly. 
 
     
     
       12. The vehicle wheel alignment system of  claim 11  wherein said visible target elements are displaced from said axis of rotation of the wheel assembly. 
     
     
       13. The vehicle wheel alignment system of  claim 11  wherein said processing unit is further configured with operating instructions to identify a nominal piercing point associated with said optical target. 
     
     
       14. The vehicle wheel alignment system of  claim 13  wherein said nominal piercing point corresponds to an intersection point in three-dimensional space between said vector corresponding to said axis of rotation and a plane corresponding to one of said surfaces of said optical target. 
     
     
       15. The vehicle wheel alignment system of  claim 13  wherein said processing unit is further configured with operating instructions to utilize said identified nominal piercing point, said established three-dimensional vector, together with a predetermined configuration of said optical target to identify a wheel center point for said wheel assembly. 
     
     
       16. A method for acquiring vehicle measurements with a machine vision vehicle wheel alignment system, comprising:
 positioning at least one imaging sensor with a field of view encompassing at least a portion of a vehicle including a wheel assembly; 
 securing at least one optical target to said wheel assembly, such that a plurality of target elements disposed on at least two surfaces of the optical target in a determinable geometric and spatial configuration are within said field of view; 
 acquiring a first set of image data from said at least one imaging sensor with said wheel assembly at a first rotational position on an axis of rotation, said first set of image data representative of at least one visible target element of each of said two surfaces; 
 rotating said wheel assembly to a second rotational position on said axis of rotation; 
 acquiring a second set of image data from said at least one imaging sensor with said wheel assembly at said second rotational position, said second set of image data representative of at least one visible target element of each of said two surfaces; 
 processing said acquired sets of image data, together with said determinable geometric and spatial configuration of said plurality of visible target elements, to identify said axis of rotation of the wheel assembly. 
 
     
     
       17. The method of  claim 16  wherein said set of securing further includes positioning one of said at least two surfaces of said optical target below, and in front of, said axis of rotation of the vehicle wheel assembly. 
     
     
       18. The method of  claim 16  wherein said processing step further includes identifying an intersection point between the axis of rotation of the wheel assembly and a plane of a surface of said optical target. 
     
     
       19. The method of  claim 18  wherein said processing step further identifies a wheel center point from said identified intersection point and said determinable configuration of said optical target. 
     
     
       20. The method of  claim 18  wherein said processing step further includes
 establishing a first line of intersection between a plane of said optical target surface at said first rotational position and said plane of said optical target surface at said second rotational position, in a coordinate system associated with said first rotational position; 
 establishing a second line of intersection between a plane of said optical target surface at said first rotational position and said plane of said optical target surface at said second rotational position, in a coordinate system associated with said second rotational position; and 
 establishing said identified intersection point as a common point on said first and second lines of intersection. 
 
     
     
       21. The method of  claim 16  wherein said axis of rotation of the wheel assembly is identified as a three-dimensional vector. 
     
     
       22. The method of  claim 21  wherein said processing step further includes identification of a nominal piercing point associated with said optical target. 
     
     
       23. The method of  claim 22  wherein said nominal piercing point is identified as an intersection point in space between said three-dimensional vector and a plane corresponding to one of said surfaces of said optical target. 
     
     
       24. The method of  claim 22  wherein said processing step further includes identifying a wheel center point for said wheel assembly utilizing said identified nominal piercing point, said established three-dimensional vector, together with a predetermined configuration of said optical target.